1. Field of the Invention
The present invention relates to a method and apparatus for manufacturing copper and/or copper alloy ingots having no shrinkage cavity inside and having a smooth outside surface without wrinkles, and, in particular, relates to a method and apparatus for manufacturing high purity copper alloy ingots with a purity of more than 99.9999% by weight, having no shrinkage cavity and having a smooth surface without wrinkles.
2. Description of the Related Art
In general, copper and/or copper alloy ingots are manufactured by casting a molten copper and/or copper alloys into an ordinary mold or into a continuous casting mold.
However, a large shrinkage cavity is normally formed at the top portion of the ingot when the ingot is manufactured by casting in an ordinary mold and the shrinkage cavity must be removed by cutting off the shrinkage cavity from the ingot, which results in reducing the material yield. When the copper and/or copper alloy ingot are manufactured by casting the molten metal into a continuous casting mold, wrinkles are normally formed on the ingot surface and the wrinkles must be removed before subsequent processing. The shrinkage cavity and the wrinkles are liable to be formed in the high purity copper and/or copper alloy ingots with a purity of more than 99.9999% by weight. Therefore, a method and apparatus for manufacturing a high purity copper and/or copper alloy ingots which include no shrinkage cavity or wrinkles is desired.
In the course of studying a method and apparatus for manufacturing a high purity copper and/or copper alloy ingots having a purity of higher than 99.9999% by weight having no shrinkage cavity and having a smooth surface without wrinkles, the following knowledge was learned.
(a) The copper and/or copper alloy ingot with a purity of higher than 99.9999% by weight obtained by the following method include no shrinkage cavities and have smooth surfaces without wrinkles. The method comprises the step of casting the molten high purity copper or copper alloys (referred to as xe2x80x9cmetalsxe2x80x9d herein) into a mold, which is installed in a heating furnace such that a bottom surface of a mold is placed on a cooled pedestal in a heating furnace and the side wall of the mold is heated by a plurality of heating elements of the heating furnace so as to form a temperature gradient in the vertical direction of the mold increasing from the bottom towards the top.
(b) The temperature at the top portion of the side wall of the mold is preferably maintained at temperatures ranging from a temperature less than the melting point of copper to a temperature 150xc2x0 C. below the melting point of copper.
The present invention has been accomplished based on the above knowledge, and the features of the present invention include the following.
(1) A manufacturing method for a copper and/or copper alloy ingot having no shrinkage cavities and having smooth surfaces without wrinkles comprising the step of casting the molten copper and/or copper alloys into a mold, which is heated, forming a temperature gradient in the vertical direction such that the temperature at the lower portion is lower and the temperature increases toward the upper portion.
In the above manufacturing method (1) for a copper and/or copper alloy ingot having no shrinkage cavities and having smooth surfaces without wrinkles, it is preferable to maintain the temperature at the upper portion of the mold within a temperature range between a temperature less than the melting point and a temperature 150xc2x0 C. below the melting point. It is more preferable to maintain the temperature of the upper portion of the mold at a temperature 90xc2x0 C. below the melting point. The reason for limiting the temperature of the upper portion within temperatures ranging from a temperature less than the melting point to a temperature 150xc2x0 C. below the melting point is that, if the temperature at the upper portion of the mold is heated above the melting point, the top of the ingot will not be solidified so that a solid ingot is not obtained to the end, and if the temperature of the upper portion of the mold is lower then the temperature below 150xc2x0 C. of the melting point, shrinkage cavities will be generated.
The features of present invention further include the following.
(2) In the manufacturing method for a copper and/or copper alloy ingots having no shrinkage cavities and having smooth surfaces without wrinkles comprising the step of casting the melt into a mold, which is placed on a cooled pedestal and which is heated so as to form a temperature gradient in the vertical direction in which the temperature of the lower portion is lower and the temperature increases toward the upper portion, wherein the temperature of the upper portion is maintained ranging from a temperature less than the melting point to a temperature 150xc2x0 C. below the melting point of the copper and/or copper alloy.